Even if you’ve never seen an episode of Breaking Bad, and the chances of that are quite high, it’s hard to be completely unaware of the huge buzz currently being generated by the its final eight episodes which have just started airing on internet streaming service Netflix. Beginning in the US in 2008, and briefly appearing on Channel 5 for two seasons before vanishing from British viewers’ sight except for box sets and illegal downloads, the show about a high-school chemistry teacher who turns to illicitdrug production after being diagnosed with cancer has become a word-of-mouth sensation.

For five years, its ever-growing viewership has followed the dark, funny and sometimes very nasty story of mild-mannered family man Walter White (Bryan Cranston) as he has evolved into an inhumanly calculating criminal mastermind.

The transformation has occurred right under the nose of his drug-cop brother-in-law Hank (Dean Norris), who has been obsessively pursuing the mysterious death-dealing figure who produces almost 100-per-cent pure crystal-blue methamphetamine.

As the show has moved on to the second half of its fifth series, expectation about the drama’s denouement has reached fever pitch. “It’s turned into a frenzy out here,” says Norris.

The cast are used to keeping tight-lipped about events, but the secrecy stakes have been raised for the finale: “By the end of the show, all the scripts had all the juicy parts redacted, they were blacked out,” says Norris. “It was like working for the CIA.”

Norris, with his stocky build and no-nonsense countenance, has for decades been a go-to guy for casting directors looking for someone to play the role of a cop, military or other authority type figure (he’s also starring in Channel 5’s Under the Dome, playing exactly this type of part). But he says this role was unlike any he had played before.

Over the seasons we’ve seen Hank battle with post-traumatic stress disorder and paralysis as he employs relentless, grinding methods refreshingly absent of the usual TV lawman glamour. “It’s funny because for better or worse that’s real police work,” he says. “It’s just poring over and poring over [evidence] and [the writers] weren’t afraid to just allow Hank to do that.”

The casting is one of the important factors in making Breaking Bad so special. There’s a mix of seasoned pros alongside newcomers such as RJ Mitte – who suffers from mild cerebral palsy and had never acted before – as White’s son Walt Jnr. Occupying the middle ground is Bob Odenkirk, who plays crooked lawyer (and fan favourite) Saul Goodman.

Odenkirk started his career writing for Saturday Night Live. Since then he’s worked on both sides of the camera, writing, producing, directing and performing, almost entirely in the comedy arena. So what was it that Breaking Bad’s creator-writer Vince Gilligan saw in Odenkirk’s CV that made him think he’d be perfect for such a serious role, albeit one with many funny moments? “He was a fan of my TV show which was called Mr Show with Bob and David (an early HBO production from 1995). It was a sketch comedy show which you guys never got over there.” Odenkirk reveals, “I never pried too hard because, obviously it’s the golden goose and I’m just thankful I got a chance to be in it. But I wonder what part of Mr Show it was that made Vince think I could do this. I thought he gave it to me because of The Larry Sanders Show (where Odenkirk played slimey manager Stevie). But no, he said Mr Show.”

Such was Gilligan’s faith in Odenkirk that he wasn’t even required to audition. Finding himself in scenes with some real acting heavyweights must have been quite a shock to the system. “Yeah, these guys are massively talented and the part is much bigger and meatier than anything I’ve done by a long way. I took it very seriously, I could see right away that I needed to pour my focus and effort into it. I certainly worked with and off Bryan Cranston, Aaron Paul (Walt’s former student turned crime partner Jessie) and Anna Gunn (Walt’s wife, Skyler), their energy and their focus raised my game.”

When Breaking Bad left us in the middle of season five, it was with a classic cliffhanger, as Hank finally put all the pieces together, his epiphany coming to him as he sat on the toilet. “That’s typical Vince Gilligan and Breaking Bad right there,” laughs Norris.

So what can we expect from this remarkable show as it bows out? Details are scant but both actors are clearly excited by what’s to come.

“It’s an incredible amount of blowback – that’s a term that Saul used in an earlier episode,” Odenkirk explains. “It is a massive shattering of this character’s world, of this universe created by Vince Gilligan. It is very surprising, you cannot tell where it’s going and it’s very satisfying and shocking. No bad deed goes unpunished is their little slogan, and boy, oh boy, is it true. Consequences everywhere, bloody, bloody, horrible consequences.”